Source not found in MAC table
mzinz
Member Posts: 328
in CCNA & CCENT
I know how simple this question is, but I've been studying for so long that I'm beginning to forget simple theories with Cisco.
A packet comes into a switch and the address destination isn't found in the mac address table.
What is done with the packet?
A. It is discarded and notification is sent to the source switch.
B. The packet is forwarded out all interfaces except the incoming int.
C. The packet is discarded.
A packet comes into a switch and the address destination isn't found in the mac address table.
What is done with the packet?
A. It is discarded and notification is sent to the source switch.
B. The packet is forwarded out all interfaces except the incoming int.
C. The packet is discarded.
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2x 2950
2x 3550
2x 2650XM
2x 3640
1x 2801
Comments
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Danman32
Member Posts: 1,243
B. Packet is forwarded to all ports (flooded) except the receiving port.
If the switch doesn't know where the destination is, that is, which port the destination MAC is attached to (directly or indirectly), it has to send it to all ports. In this case it acts like a hub.
As a matter of fact, a technique a hacker might use to force a switch to start acting like a hub is to jam as much garbage MACs he can into the switch's table, that it has no choice but to flood frames to all ports, including the one the hacker is sitting on.